Multiple gap arc interrupter



June 21, 1949. R. R. PITTMAN 2,473,819

` MULTIPLE GAP ARC INTERRUPTER u.ned July 12, 194e Fig.

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INVENTOR Patented June 21, 1949 UN I TED:l STAT ESI PAT ENT OFFICE MULTIBBE GAB-ARC INTERRUPTER.

Ralph 3.1 Pittman, NorthALittleARock, Ark. Application'Julyj` 12; 1946, Serial No. 68,2;989V4 8 Claims.

This invention relates to excess-voltagelprotecf.

voltage.r

Amongthe objects; of the: inventiontmay be notedw). theA provision of a sparkover. ormdischarge path Whicli-y includesA in series circuit ar,-

rangement. alpluralityeof:spark,-.gaps so fcooperatl inglwithpther elements ofthe construction that under-voltage. stress .thesumbf thevoltagesv ap-..

pearingacross the individual gaps `greatly v exceeds the voltage impressed.. across :the device; (b), the l provision of a r`construction in which4 the, division of 1voltagebetWeen the,y serially arranged gaps t remainssubstantiallyconstant regardless oft rate of. change inapplied, voltage; (c) thepr.ovision.

of a construction in which sparkover of a sui; cient number of gaps, to effect arc extinguishment is accomplished ataprotective voltage level much less than is possible Witha simple series arrangement of gaps, vvthoutmore, connected to bridge the circuit; (e) the provision of a multiple gap arc interrupter having spark gaps in series in whichrrai definite l.voltage'may belmadeito` appear concurrentl `across. each ofthe .multiple-gaps when a predetermined voltage is impressed across the'terminals: of the device; the definite voltage across each gap being only slightly less thanthe- Bllgingwfollowing; sparkover,l The. impedance drop attendingfthe passageof the surge current through. thefresistancefis v:impressed uponlthe vconnected terminal voltage;l (flthe-provision of a device embodying: aseries .of spark-:gaps infwhicn sparkover. of. all xgaps-occursconcurrex-itly,r as 1a` opposed to the cascade type of iiashover commoninimulf.

tiple series gap devices; (g) a device embodying a lplate condenser-With serially, arranged plates in which the respective plates of the condenser are formed to provide a series-of, sparkgapsrfrom one `endy plate ofthefcolldensen to the other., the gaps so cooperating vvithmthe condenser plates that the latter are serially connected in response to sparkover in a manner ,diiiering from the seriatim order of platesfrom one end of the condenser to the other; and (h) the provi-sion otra,-v

construction requiring only simple and inexpensive parts and assembly. Other objects and advantages will appear from the following description.

The invention is exemplified by the form, combination and relationship of the parts shown in the accompanying drawingand described in the specification, and the scope-of the invention is particularly pointed out in the appended claims.

In its broadest aspect; thecircuit arrangement of the invention is similar in some respects to the 25,5circuits?,include..onevfspark` gap, functioning to.A

gytioniftthe resistanceistoo.great. .or the thermal, f destruction cfr-the,y resistance` element if the reconstruction :shown in -my copending application Seria-lfNo:666;902,. 1iled;Mayl 3, 1946-, which has matured into Patent No. 2,427,975, September 23,

Eig; 1 of: the-;drawing` is,y anv elevation, shown v, partly insection of an` embodiment of the invention; Figsi 2 and=3,l are; respectively sectional views taken along-.thelinesZf-Zz; andi-320i Fig. 1;k Fig. 4 is a fragmentary sectional view showingvthe lrelationship of the.v conducting members to thefinsulating members; and Figs. 5; 6 and 7 shown diagrammaticallywthe circuit arrangement or equi-valent Y circuitarrangement ofthe structure. c

Asi-the drawing. shows, the embodiment presentedvhere is particularly -adaptedifor limiting excessrvol-tagagsuch as mightI be caused byV light-U ning; of low orf-.sofcalledutilization voltage circuits?, e .;-,g.120f-240f-480f650 volts, but it will appear.` that-`4 the: rangef-of application may, .be extended to, higher circuit voltages by simply adding5additional elements in quantities f greater than t illustnated. A

Currently Iowa-voltage, lightning. arresters or bye-passC devicesdesigned for application to power prevent-leakage. currennundervnormal conditions, andi an i are extinguishing. element having resistance for limitingl thepowen follow current to as sufficiently.l small valuetoprevent sustained arcapparatus, in sometcases resultngviny connected apparatus iiashing over. or puncturing of insula- Thepresent, invention` provides. av constructionembodying, not resistance, element, substituting 403;;thereforatnovel arrangement. or elementsinclud ingw azseresarrangenfielfl't,=ofI arcingl gaps` to causef.

araV extinguishmentwithout practicalsacrice A ofprptectiveilevel.. Itiswellknown that a seriesof I,short,arcsrequiresmuch Amore voltage tov sus- 45nftaln rthan.,atsingleam .of much greater lengthand-:this .principle ofarc extinguishmentis utilized inzthefpresentinvention, However, win construc-v` elementsbut.xlackng the novetieatures 0f. the., present iinfeiitrm ywhichenalol,es anatual t total vltageiappled tot the. gaps greater. than. tha` tfinipresseds vtltage,fa,c onClitiQrlE entirely distinguished from that of simply unbalancing the voltage applied to the individual gaps without any increase in sum.

Referring to Figs. 1, 2, 3, and 4, the embodiment of the invention shown includes a plate condenser comprising a stack of six plates of conducting material, consisting of the end or terminal plates I5 and 20, the centrally positioned pair of plates I1 and I8, and the intermediate plates I6 and I9. Each plate is insulated from every other by means of a disk of insulating material, the insulating disk 23 being interposed between the first and second plates, the disk 24 between the second and third plates, the disk 25 between the third and fourth plates, the disk 26 between the fourth and fifth plates, and the disk 21 between the fifth and sixth plates. The conducting plates and insulating disks are rigidly held in parallel abutting stacked relationship by means of the bolt 3| and cooperating nut 32, the bolt 3| extending coaxially through the stack, and being insulated from the conducting plates by means of the sleeve of insulating material 35.

The terminal plates I5 and 20 are provided with upwardly extending portions to which the terminal conductors 2| and 22 are respectively connected, as by soldering at 28 and 29, and the block of insulating material 30 spans the terminal conductors.

The assembly just described is contained in a housing of conducting material, including the hollow body portion 36 and the cover 31, the conductors 2| and 22 extending outwardly through the threaded nipple 38. For holding the assembly in spaced relationship with the wall of the hollow body portion 36, a plate of insulating material 34 is clamped between the head of the bolt 3| and the end plate I5, the plate extending outwardly beyond the plate assembly and being contoured to fit the inner surface of the body portion 36. A spring 33, of conducting material, is clamped between the terminal plate 20 and the nut 32, extending laterally on each side thereof and outwardly to engagement with one at wall of the body portion 36, resiliently holding the head of the bolt 3| against the other at wall of the body portion, thereby electrically connecting the terminal plate 20 to the body portion.

By means of suitably formed outwardly extending integral portions of the conducting plates, peripherally spaced spark gaps, positioned outwardly beyond the edge of the insulating disks, are provided. The plate I9 is provided with diametrically opposed outwardly and laterally extending portions, the respective ends of which extend near and in spaced relationship with outwardly extending portions of the plates I5 and I1, to provide the spark gap I0 between the plate I9 and the plate I5, and the spark gap I3 between the plate I9 and the plate I1. Similarly, along a diameter 60 degrees displaced from that of the outwardly extending portions of the plate I9, the plate I6 is formed with diametrically opposed outwardly and laterally extending portions, the respective ends of which extend near and in spaced relationship with outwardly extending portions of the plates I8 and 20, to provide the spark gap II between the plate I6 and the plateV 20, and the spark gap I2 between the plates I6 and I8. The plate I1 is provided with a single outwardly and laterally extending portion, the end of which extends near and in spaced relation ship with an outwardly extending portion of the plate I8, to provide the spark gap I4 therebetween.

It may be noted that a construction as above described will yield the circuit arrangement dagrammed in Fig. 5. If the device is applied for the purpose of limiting the voltage of a conductor to ground, the terminal conductor 2| would normally be connected to the conductor the voltage of which it is desired to limit, and the terminal conductor 22 grounded. The insulating elements of the structure must be so coordinated with the conducting elements that sparkover occurs only via the spark gaps.

In addition, for proper operation of the device, cascade sparkover should be avoided; i. e. all of the gaps should sparkover at the same instant rather than an initial breakdown of one being relied upon to cause another to sparkover, which is a common occurrence in structures heretofore having capacitatively or otherwise unbalanced serial gaps.

Reference is made to Fig. 6 for the purpose of illustrating the manner in which device functions to accomplish concurrent sparkover of the serial arrangement of gaps. Fig. 6 is an equivalent circuit in which the condenser A may represent capacitance provided by the plates I5 and I6 and the insulating disk 23 therebetween; the condenser B the capacitance provided by plates I6 and I1 and the insulating disk 24 therebetween; the condenser C the capacitance provided by the plates I1 and I8 and the insulating disk 25 therebetween; the condenser D the capacitance provided by the plates I8 and I9 and the insulating disk 26 therebetween; and the condenser E the capacitance provided by the plates I 9 and 20 and the insulating disk 21 therebetween.

The plates of the condenser and the thickness and character of the insulating material therebetween, may be as a convenient practical design, such that the equivalent capacitances of Fig. 6 are:

A-128 mmf. B-128 mmf. C-B mmf.

D-128 mmf. E-128 mmf.

When a voltage E is applied at the terminals, Ea plus Eb plus Ec plus Ed plus Ee=E (l) Since equal voltages appear across equal capacitances,

Ea=Eb=Ed=Ee (2) And since voltage division across unequal capacitances in ser1es is an inverse function of the capacitances,

lr6-1% Ea: 16E@ 3) Solving for Ea in (1) Ea plus Ea plus 16Ea plus Ea plus Ea=E, or 20Ea=E E Eil-2 0 and E Eb- 16E EC-o E Eri- 2 0 E Evevltagejacmgsigapam are serially connecteddn, series-with.. the group;

consisting ,of'allLof'the even numberedcondenser plates.

It .maybe noted thatsthecapacitance resulting. from the. cooperation. ofthe .centrally positionedr plates( I I and. i8) i, withthe `interposeddnsulating material .'is. common torallfof/the spark-gaps. If v'tliedimensions .of 'the structure. areY such that. this capacitance is substantially smaller-.thanthat:4 of the condensersv on.v each; side f ofy the vvcentrallyf positioned vplates, .thenincremefnt involtage added.y to each. of'. thegapsfwhichr-span one ormore of; the v.last-named condensers will be small, and .,the.

sparkover. voltage-of. ,the entire.V seressof.l gaps ,.ap.-

proaches that. of the .sparkover voltagevof. the centrally-positioned.,gap.

For certaindow voltage. applications; theinter V50..1 required.. Eor such-aconstruction,itwill bev clean rupting. abilityv on three spark. gaps issallthat is that a four plate device, such as that shown-diem agrammatically lin 'Eiga-7,' will result by simply utilizing the intermediate plates IG and I9 as the terminal platesgvfan'dr omitting;the plates l5 and 20,` along., with the insulatingv4 disks. 23 and. 2.1. This modification yields/theV circuit. of Fig. '7, in. which the terminal conductors 39`and40'are respectively connectednt'o. the terminal'lplates 4I and 44. The pair of centrally., -positioned plates: areindicatedat 42 and 43, .andthe voltagesresponsive serialA arrangementv of..gaps andi-plates is, as above indicated, from the terminal conductor 39 throug-h'thevplateM; vthence through througlnthegap 46, thence.- throughfthe plate. 42, thence through the gap 41 to the plate 44, and through the latter to the other terminal conductor 40.

For best operation, it is desired that the voltage appearing across each gap reach the sparkover magnitude of all of the respective gaps concurrently, which is easily accomplished in the construction illustrated by simply regarding the coordination of the gaps with the condenser elein` which "series arrangement thev group,Y consist- "V- ing of 'allof'th'e odd. numbered condensen plates mentsfbridged thereby:- Itawillbe clear fromfth'e above description a that athis; can be accomplished 1` with. anyeven numberfof condenser plates greater thanffour,.and that in such a construction,- the number offsparkwgaps. which can be effectively used, is.'on.e; less.than.-the number of plates of thestructure.

Inavlewfofr thefaboveconsiderations, it is invtendedrthatltheienflbodiments here described will 10i befregarded as 1 illustrative rather than limiting constructions.

I: claimy as my invention:

A1. Ani-aroi'interrupter comprising a plate `con-v denserfhavingi-an even-f number oi? atleast four normally-insulated conducting plates including a centrallyi-positionedn pair of plates and an additionahplate4 positi'onedadjacentto and at each side offfsaidpair.of=plates, said plates being formed toi-provide; a` iirst spark gap between said cen- "trallyp'ositioned pair of plates, a second spark gapibetween onefa'dditional plate and that plate ofisaid pair mosti-remote' therefrom; and a third sparkf'gapbetween the other 'additional plate and the.' otl'ierplateof said\ pair, the series arrangementoffsaidsparkigaps and' said centrally-posi-v tione'dplates: constitutingV a series circuit including thethreespark 'gaps' 4from said one additional plate't'o the'- other, saiolspark4 gaps being dimensione'clt'o'provid'e the weakest electrical path from said"lone-additionalplate to the other, and the' capacitancesl as measured between eachV addiy tional platef'andi-'the respective centrally-positioned''platebeingf substantiz'tllyv equal and each capacitance being substantially greater thanthe 35;"capacitance asfmeasuredfbetween said centrallypositionedplates.'

2'.l An 'arc interrupter comprising a stack of normally' insulatedi'conducting plates including l a pair of end plates andltwo centrally-positionedv plates, each ofisaidplates'having an outwardly ex'tendir'igfportion formed to provide spark gaps between certain' of said' plates for establishing a circuit whichincl'udes said spark gaps in series arrangement from oneend plate to the other,

two of said lgaps' being positioned respectively' between the end plates and the respective remotest centrally-positioned plate, and one gap being positioned between the centrally-position'edv plates, the arrangement lbeing such that the weakest'electrical path from one end plate to the otherA is via said dielectric circuit, and the capacitance between'said,centrally-positioned plates is .smallin .comparison with .the capacitance between each .endplate and the. respective adjacent oentrallyrpositioned plate.

3..An. arc. interruptercomprising a stack ,in-

cludingaat leastfour. normally insulated plates.A of conducting material oonsistingof a rst plate,

a secondiplater athirdplate and a fourth plate,

insulating-material.interposed between the first plates and thef second .plate,.finsulating material. inter-posedbetweentlie :third .plate and the fourth plate, and insulating materialinterposed between. the gages, thence through the: plate 43, thence iiftheseconm platefandthethird plate, said lastnamedfinsulating-smaterial cooperating with saidf secondand-thirdplate toprovide a capacitance substantially less than that provided by the cooperation of the insulating material with either the first and second plates or the third and fourth plates, means holding said plates in substantial coaxial alignment, and integral portions of said plates extending outwardly beyond said insulating material and arranged to form a spark gap between said second and third plates, a spark gap between said rst and third plates, and a spark gap between said second and fourth plates, the arrangement being such that sparkover between said first and fourth plates occurs preferentially through the series of the three spark gaps.

4. An arc interrupter comprising a stack of at least four normally insulated plates of conducting material including a serial arrangement of a first plate, a second plate, a third plate and a fourth plate, insulating material interposed between the iirst plate and the second plate, insulating material interposed between the second plate and the third plate, and insulating material interposed between the third plate and the fourth plate, said last-named insulating material cooperating with said last-named plates to provide a capacitance substantially equal to that provided by the cooperation of said rst-named insulating material with said rst and second plates and substantially greater than the capacitance resulting from the interposition of said insulating material between said second and third plates, means holding said plates in substantial coaxial alignment, and integral portions of said plates extending outwardly beyond said insulating material to form a series circuit arrangement which includes serially three spark gaps between said first plate and said fourth plate, said spark gaps being arranged to connect, in response to sparkover thereof, all of said plates in the series circuit arrangement in which said rst plate connects to said third plate, said third plate to said second plate, and said second plate to said fourth plate.

5. An arc interrupter comprising a container of conducting material, a plate condenser therein having an even number of at least four conducting plates mounted in insulated relationship one to any other, said plates including a centrally-positioned pair of plates providing a predetermined capacitance there-between and terminal plates at the respective outer sides and adjacent to said pair of plates providing respective capacitances substantially greater than said predetermined capacitance, said plates being provided with outwardly extending portions formed to provide a spark gap between said centrally-positioned pair of plates, a spark gap between one terminal plate and that plate of said pair most remote therefrom, and a spark gap between the other terminal plate and the other plate of said pair, the series arrangement of said gaps establishing the weakest electrical path through said plates from one terminal plate to the other, means holding said plates in spaced parallel relationship, insulating means isolating one terminal plate from said container, and conducting means connecting the other terminal plate to said container.

6. An arc interrupter comprising a series of parallel conducting plates including a rst, second, third, fourth, iifth and sixth plate, insulating material spacing said plates apart in normal insulated relationship, means insulated from said plates holding said plates in fixed position, peripherally spaced spark gaps associated with said plates arranged to provide a series arrangement of spark gaps consisting of a spark gap between the iirst plate and the fifth plate, a spark gap between the fifth plate and the third plate, a

spark gap between the third plate and the fourth plate, a spark gap between the fourth plate and the second plate, and a spark gap between the second plate and the sixth plate, said spark gaps being arranged to establish a preferential electrical path between said iirst plate and said sixth plate which includes in series circuit relation all plates therebetween, the plates so co-operating with the interposed insulating material that the capacitances between the rst and second plates, the second and third plates, the fourth and fth plates, and the fifth and sixth plates are substantially equal and each substantially greater than the capacitance between the third and fourth plates.

7. An arc interrupter comprising a stack of n parallel plates, n being an even number greater than two, said stack including a centrally-positioned pair of plates, insulating material spacing said plates apart in normally insulated relationship, means holding said plates in said insulated relationship, conducting means including said plates providing a preferential sparkover path from one end of said stack to the other, said sparkover path including at least three spark gaps connected in series circuit relationship from -one end of said stack to the other and so related to said conducting plates that the capacitance formed by the cooperation of said centrally-positioned plates with the insulating material therebetween is common to all three spark gaps, and substantially less than the capacitance formed by any other adjacent plates in co-operation with the insulating material there-between.

8. An arc interrupter comprising a stack of normally insulated plates of conducting material,

,one of said plates co-operating with another adjacent plate to provide a predetermined capacitance therebetween and the remaining plates cooperating with respective adjacent plates to provide a plurality of substantially equal capacitances each substantially greater than said predetermined capacitance, and integral portions of said plates extending outwardly to form a series circuit arrangement including all of said plates and a plurality of spark gaps there-between, the -arrangement being such that at least said predetermined capacitance is connected across each spark gap.

RALPH R. PITI'MAN.

REFERENCES CITED The following references are cf record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 444,678 Thomson Jan. 13, 1891 1,683,590 Atherton Sept. 11, 1928 FOREIGN PATENTS Number Country Date 40,108 Switzerland Apr. 22, 1907 

